A NATIONAL HISTORIC CHEMICAL LANDMARK PRODUCTION OF ALUMINUM METAL BY ELECTROCHEMISTRY OBERLIN, OHIO SEPTEMBER 17, 1997 AMERICAN CHEMICAL SOCIETY Division of the History of Chemistry and The Office of Public Outreach his booklet commemorates the designation of the production of aluminum metal by electro - chemistry as a National Historic Chemical TLandmark. The designation was conferred by the American Chemical Society, a nonprofit scientific and Sketch of the woodshed laboratory by Julia Severance, made while Hall was alive. educational organization of more than 152,000 chemists and chemical engineers. A plaque marking the designation was presented to Oberlin College on September 17, 1997. The inscription reads: “On February 23, 1886, in his woodshed laboratory at the family home on East College Street, Charles Martin Hall succeeded in producing aluminum metal by passing an elec - tric current through a solution of aluminum oxide in molten cryolite. Aluminum was a semiprecious metal before Hall’s discovery of this economical method to release it from its ore. His invention, which made this light, lustrous, and nonrust - ing metal readily available, was the basis of the aluminum industry in North America.” Acknowledgments: The American Chemical Society gratefully acknowledges the assistance of those who helped prepare this booklet, including: Norman C. Craig, Robert and Eleanor Biggs Professor of Natural Science, Oberlin College; Lewis V. McCarty, retired Research Associate, Inorganic Chemistry, General Electric, Nela Park, Cleveland, Ohio; Roland M. Baumann, Archivist, Oberlin College; On the Cover: (Clockwise) C. M. Hall, and Peter J. T. Morris, Science Museum, London, the National Historic 1885; Hall reading American Chemical Chemical Landmarks Program Advisory Committee liaison. Journal , about 1905; F.F. Jewett, Hall’s mentor; Hall family home and woodshed. This booklet was produced by the ACS Office of Public Outreach. Background: Letter from Hall to his Layout: Dahlman Middour Design. Copyediting: Elizabeth A. Mitchell, ACS. brother February 24, 1886. Photographs courtesy of Oberlin College and the Aluminum Company of America. Background (this page): Diagram from C.M. Hall’s patent. Copyright © 1997 American Chemical Society CHARLES MARTIN HALL SOLVES THE ALUMINUM CHALLENGE From Semiprecious to became well acquainted with cur - Abundant rent European science and became interested in the Before 1886, aluminum was a semi - promise of aluminum. He met precious metal comparable in price to silver. Professor Friedrich Wöhler, Although the element had been discovered in who had isolated aluminum as 1825 and had been investigated by many a metal in 1827 following European scientists, the only way to prepare H. C. Oersted’s lead in 1825. the metal was by the complex and difficult Before Jewett returned to process that culminated in reacting metallic America in 1875 to become sodium with aluminum chloride. When the Oliver Wolcott Gibbs’s private Washington Monument was completed in 1884, a assistant at Harvard University, he 6-lb pyramid of this costly aluminum was placed as obtained a sample of aluminum an ornament at the very top. It also served as the Frank Jewett at about 40 metal. In 1876, he was nomi - years of age when Hall tip of the lightning rod system, a practical applica - made his discovery. nated by the president of Yale to tion of the high electrical conductivity and corro - teach science at the Imperial sion resistance of this remarkable metal. However, University in Tokyo, where he was one of a small economical methods were needed to wrest alu - group of Westerners. In 1880 at the age of minum from its abundant minerals, which Henri 36, Jewett became the professor of Sainte-Claire Deville, the great French chemist, chemistry and mineralogy at Oberlin observed “could be found in every clay bank.” College. Two men with a common interest in alu - Charles Martin Hall first minum metal met on the campus of Oberlin College learned chemistry as a serious- near Cleveland, Ohio, in 1880. Frank Jewett was a minded youth in the town of world traveler and as well educated in chemical sci - Oberlin by reading an 1840s ence as any American academic of his day. Charles textbook he found on the shelves Hall was a local youth, self-educated in science, who of his minister father’s study. He hoped to become a successful inventor and entrepre - also carried on experiments at neur. Their association over the next five-and-one- home, the beginning of a lifelong half years led to the discovery of a practical process enthusiasm for experimental work. for making aluminum from its ore by an electric cur - An avid reader in many fields, he rent. Within three more years, Hall was producing eagerly followed the popular invention pure aluminum metal on an industrial scale. literature in Scientific American . Hall C. M. Hall at graduation from Oberlin College, 1885. Aluminum, the curiosity, became a widely used was already intrigued by the romance material, and the younger man achieved his goal of of aluminum when, as a 16-year-old a financially successful career in technology and freshman at Oberlin College in the fall of 1880, he industry. went to the chemistry laboratory to obtain some items for his home laboratory. There he met Professor and Student Professor Jewett. Frank Fanning Jewett received his undergradu - ate education and did some graduate work in chem - istry and mineralogy at Yale University. From 1873 to 1875, he continued his chemistry studies at the University of Göttingen in Germany. There he 1 THE CHALLENGE all took his first formal course in chemistry as he passed a current a junior in college. Earlier, with Jewett’s guid - through aluminum Hance and encouragement, he had worked on fluoride dissolved in aluminum chemistry and other projects in Jewett’s lab - water. Unfortunately, oratory and in his own laboratory at home. He heard this system produced Jewett lecture on the chemistry of aluminum, display only unwanted hydro - his sample of the metal, and predict the fortune that gen gas and aluminum awaited the person who devised an economical hydroxide at the nega - method for winning aluminum from its oxide ore. To a tive electrode. fellow student, Hall declared that he intended to be Julia B. Hall in 1881. After graduation, that person. Julia helped her brother by Hall continued the After many unsuccessful experiments with preparing chemicals such as work in the woodshed aluminum oxide. She had studied chemical methods of reducing aluminum ores to the chemistry and followed his behind his family’s metal, Jewett and Hall turned to electric current to experiments closely. Through house. He experi - most of his life, Hall maintained provide the powerful reducing conditions that were a lively correspondence with his mented with molten needed. To obtain electricity in a college town in sister and other family members. fluoride salts as water- Julia saved many of these letters the 1880s, one had to assemble batteries. Hall and and some of his notebooks, free solvents. He knew Jewett used Bunsen–Grove cells, which consist of a which provide an exceptional that the fluoride salts record of the day-to-day life of large zinc metal electrode in a sulfuric acid solution an inventor. had the advantage over that surrounds a porous ceramic cup containing a previously studied chlo - carbon rod immersed in concentrated nitric acid. ride salts of not absorb - Assembling enough of these cells to provide suffi - ing water from the air. Hall was aware of Richard cient electrical energy for aluminum production was Grätzel’s success in obtaining magnesium metal by using an electric current in a magnesium chloride melt as reported in the Scientific American in 1885. To work with molten fluoride salts, he needed a furnace capable of producing and sustaining higher temperatures than the coal-fired furnace of his ear - lier experiments. For this purpose, Hall adapted a second-hand, gasoline-fired stove to heat the inte - rior of a clay-lined iron tube. Despite the higher temperature of this furnace, he was unable to melt calcium, aluminum, or magnesium fluorides. Potassium and sodium fluorides melted but did not dissolve useful amounts of aluminum oxide. Hall moved on to experiment with cryolite (sodium aluminum fluoride) as a solvent. He made Hall family home with attached woodshed. cryolite, found that it would melt in his furnace, and showed that it would dissolve more than 25% by a large undertaking. The eventual laboratory process weight of aluminum oxide. The melting point of used about 1 lb of zinc electrodes, hand cast by Hall, cryolite is 1000 ˚C, an exceptionally high tempera - to obtain 1 oz of aluminum. ture for electrochemistry. He did this crucial experi - Hall did the first experiments with electricity ment early in February 1886 and repeated it the in Jewett’s laboratory during his senior year of next day for his sister Julia to witness. 1884–85. He prepared aluminum fluoride from haz - Six days later, Hall first attempted to prepare ardous hydrofluoric acid in special lead vessels, and aluminum metal by passing an electric current 2 through a solution of aluminum oxide Letter from C. M. Simultaneous Hall to his brother in molten cryolite. He immersed George written the graphite rod electrodes into the fiery Discoveries day after the discovery. solution in a clay crucible and let the How could it be that Paul current run for a while. In Julia’s pres - Héroult in Paris, France, and ence, he poured the melt into a frying Charles Hall in Oberlin, Ohio, pan and broke apart the cooled mass made nearly simultaneous, yet but found no aluminum. There was independent discoveries of the only a grayish deposit on the negative Diagram from patent No. 400,664. same process of refining alu - electrode, a deposit that did not have minum? Many factors seem to the shiny metallic appearance of aluminum.